What parts of your body benefit while bike riding?

What parts of your body benefit while bike riding?
I'm looking to slim down my thighs a bit and I'm not sure if bike riding helps the thigh area at all.

The bike certainly helps the thigh area, but also the calfs and your waist. If you are thinking of using a still bike where you pedal and move arm bars too - that helps your arms. Your bum could also be at benefit

depends what you want to train if you want to train your legs is better driving up hill if you want to train reaction skills go down hill and if you are an adventurer go like in the wield for example off road and if you want to train speed you can just on flat land... if you are one of the people that likes to do tricks go to a bike park.

If you're trying to build muscle in the legs and lose fat, your best bet is off-road bike riding, like mountain biking in hilly areas. Biking by itself is great cardiovascular exercise, but adding hills adds resistance, which works your leg muscles and ultimately burns fat. Riding bikes also has the benefit of being much easier on your joints than jogging.